This invention relates generally to starting single phase motors and more particularly to starting capacitor start, capacitor start-capacitor run and split phase motors using solid state apparatus and techniques.
Such motors conventionally have been started using electromechanical relays or centrifugal switches. These devices are generally effective and are of relatively low cost but they suffer from certain inherent limitations. For example, since these devices have moving parts their longevity is limited thereby. Further, they are generally susceptible to being affected by dirt and chemical substances which may happen to be in their environment and they may also be sensitive to vibration. The most serious limitation however is the need to select and calibrate such devices for each motor rating.
It is an object of the present invention to provide a starting system and method for a single phase induction motor which can be used with a wide range or motor ratings, for example, from a tenth of horsepower up to approximately five horsepower.
Yet another object is the provision of a starting system and method which can be used with split phase motors as well as capacitor start and capacitor start-capacitor run motors.
Another object of the invention is the provision of a system which is reliable and long lasting.
Still another object of the invention is the provision of a starting system which will provide restart capability, prevent overloading of the start winding and be insensitive to line voltage variations.
Another object of the invention is the provision of a system that can readily replace existing systems, as a service part of as an original component, without significant modifications of the motor.
Various additional objects and advantages of the present invention will become readily apparent from the following detailed description and accompanying drawings.